She’s liked him since six months.

When you start work?
I’ve been knowing her for three months

i)What the mistake is.
ii) Why you think it has been made.
iii) How you would explain and correct the mistake with a student.

Here are the corrected sentences:

She has liked him for six months.
When do you start work?
I've known her for three months.

Now ... how will you answer the three questions for each sentence?

i) The mistake in the given sentences is the incorrect use of "since" and "for" in relation to the duration of time.

ii) The mistakes have been made because the incorrect prepositions "since" and "for" are used to indicate the duration of time when they should be used in the following way:
- "since" is used to indicate a specific starting point in time, such as "since 6 o'clock" or "since Monday."
- "for" is used to indicate the duration of time that has passed since the starting point, such as "for 6 hours" or "for three days."

iii) To explain and correct the mistake with a student, you could say:
"The mistake in the given sentences is related to the use of 'since' and 'for' in expressing the duration of time. 'Since' is used to indicate a specific starting point, while 'for' is used to indicate the duration that has passed since that starting point.

For example, instead of saying 'She's liked him since six months,' we should say 'She's liked him for six months,' as 'for' indicates the duration of time that has passed since she started liking him.

Similarly, instead of saying 'I've been knowing her for three months,' we should say 'I've known her for three months,' as 'for' is used to express the duration of time."

By explaining the correct usage and providing examples, the student can understand the difference and avoid making the same mistake in the future.

The mistake in the given sentences is the use of "since" instead of "for" to express the duration of time.

i) The mistake is using "since" instead of "for" to indicate the duration of time.

ii) This mistake may have been made because the word "since" is often used to indicate when an action or event started, but it is not commonly used to express the duration of time.

iii) To explain and correct this mistake with a student, you can use the following approach:

First, explain the difference between "since" and "for" in terms of expressing duration.

- "Since" is used to indicate a specific point in time when an action or event started. For example, "I have known her since 2010" means that the person started knowing her in 2010.
- "For" is used to indicate the duration of time that an action or event has been going on. For example, "I have known her for 10 years" means that the person has known her for a duration of 10 years.

Next, provide examples to clarify the correct usage of "for" when expressing duration:

- "She has liked him for six months" would be the correct way to express that she has liked him for a duration of six months.

Lastly, encourage the student to practice using "for" correctly when expressing durations of time in their writing or speaking. Offer them some exercises or additional sentences to practice using "for" correctly.